1. Field of the Invention
This invention relates generally to electronic fever thermometers.
2. Description of the Prior Art
Fever thermometers are used to measure the temperature of the human body. Ordinary mercury thermometers in which the temperature is determined by expansion of mercury, as well as electronic thermometers, are known. The temperature is converted to an electrical signal in an electronic thermometer by an electronic component. Heat-dependent electrical resistors are generally used.
Such fever thermometers must meet various requirements primarily when used in the clinical field.
Since thermometers are often destroyed or stolen, the lowest possible manufacturing costs must be considered. Such thermometers must also have a surface that is easy to disinfect and one that exhibits the least possible vulnerability to breakage, as well as guarantee good watertightness and reliable function.
Ordinary mercury thermometers in which the mercury column is integrated in a glass enclosure have satisfactorily met these requirements thus far. However, a problem in mercury thermometers is the toxicity of mercury. Old mercury thermometers are in large part responsible for the amounts of mercury deposited in the environment (for example, at landfills).
Thermometers with gallium solutions are also known. However, such thermometers are relatively expensive and are not unobjectionable in terms of toxicity. The temperature display must also be reset by shaking, which requires considerable expenditure of force in the light gallium solutions.
Ordinary electronic fever thermometers are beset with the drawback that breaks in the surface exist between the housing and the opening inserted in it for the viewing temperature reading, which poses problems with respect to sealing and disinfectability.
An electronic fever thermometer is known from DE 42 13 034, which has a hermetically sealed, air-permeable, windowless bulb in which a solar cell is provided as the power supply. A shortcoming of this thermometer is that the manufacturing and material costs are too high. Moreover, the electronic components are visible, which imparts an unattractive appearance to the thermometer.
An electronic fever thermometer is also known from WO 92/16821, which has a hermetically sealed glass housing. The visibility of the electronic components, as well as the vulnerability to breakage, are also a drawback of this known thermometer.